1. Field of the Invention
The present invention relates to a brushless motor apparatus in which a driving voltage drop caused by an internal resistance of a switch and a resistance of lines is reduced.
2. Description of the Related Art
Motors are used in a variety of industrial fields. Smaller motors are used in, for example, cellular phones, tape recorders and DVD apparatuses. Larger motors having a diameter of several meters are used for, for example, rolling mills.
Motor apparatuses are available in various types including, for example, rectifier motor apparatuses, inductance motor apparatuses, and brushless motor apparatuses.
A rectifier motor apparatus includes a brush, a rectifier and a coil. Rectifier motor apparatuses, which have a simple structure and usable with DC or AC currents, are widely used in, for example, multi-purpose compact devices, electric home appliances and toys.
In an inductance motor apparatus, a motor is rotated by a current which is generated by electromagnetic inductance caused by rotation of a magnetic field. Inductance motor apparatuses are used in, for example, manufacturing machines such as rolling mills for steel, paper and the like.
A brushless motor apparatus includes a motor rectifying mechanism using a sensor or dedicated IC, instead of a mechanical sliding member such as a brush, a rectifier and the like, unlike a rectifier motor apparatus. The brushless motor apparatus, which does not include a brush or a rectifier, naturally does not cause contact and thus does not cause friction between a motor with the brush or rectifier. Therefore, the brushless motor apparatus has a longer life than other types of motor apparatuses and does not suffer from the inconvenience of metal or carbon powder being scattered. Brushless motors are used in, for example, hard disc drives and CD-ROM drives of personal computers, and air cooling fans.
A brushless motor apparatus including three-phase coils connected in a Y or star shape (Y-connection three-phase brushless motor) is conventionally known. However, there is no brushless motor apparatus existing having three-phase coils connected in a delta shape (delta-connection three-phase brushless motor), since the delta connection is mostly used for rectifier motors and induction motor apparatuses.
A brushless motor apparatus according to the present invention includes a motor section including delta-connected three-phase coils; a switching section electrically connected to the motor section by a line; and a driving section for controlling an ON state and an OFF state of the switching section so as to drive the motor section. r1+r2 less than 2R, where r1 is an internal resistance of the switching section in an ON state, r2 is a resistance of the line connecting the motor section and the switching section, and R is a direct current resistance of each of the three-phase coils.
In one embodiment of the invention, the driving section controls a ratio between a time period in which the switching section is in the ON state and a time period in which the switching section is in the OFF state to be variable.
In one embodiment of the invention, the motor section includes a rotor rotatable about an axis thereof. The driving section controls the ON state and the OFF state of the switching section so that the switching section outputs a sine wave current in accordance with a rotation angle of the rotor.
In one embodiment of the invention, the motor section and the switching section are integrally structured.
In one embodiment of the invention, the motor section further includes a magnetic flux detection section for detecting a magnetic flux generated by the rotor. The magnetic flux detection section is provided at a position at which magnetic fluxes generated by two adjacent coils among the three-phase coils counteract each other.
In one embodiment of the invention, the motor section further includes a magnetic flux detection section for detecting a magnetic flux generated by the rotor. The driving section controls the ON state and the OFF state of the switching section so that a difference between a phase of the sine wave current and a phase of the rotation angle of the rotor detected by the magnetic flux detection section is maintained.
In one embodiment of the invention, the motor section further includes a magnetic flux detection section for detecting a magnetic flux generated by the rotor. The driving section controls the ON state and the OFF state of the switching section so that a difference between a phase of the sine wave current and a phase of the rotation angle of the rotor detected by the magnetic flux detection section is variable.
Thus, the invention described herein makes possible the advantages of providing a delta-connection three-phase brushless motor having superior characteristics to those of the conventional Y-connection three-phase brushless motor.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.